Update dependencies (#886)

vendor/github.com/nlopes/slack/backoff.go

@@ -1,7 +1,6 @@
 package slack
 
 import (
-	"math"
 	"math/rand"
 	"time"
 )
@@ -14,41 +13,42 @@ import (
 // conjunction with the time package.
 type backoff struct {
 	attempts int
-	//Factor is the multiplying factor for each increment step
-	Factor float64
-	//Jitter eases contention by randomizing backoff steps
-	Jitter bool
-	//Min and Max are the minimum and maximum values of the counter
-	Min, Max time.Duration
+	// Initial value to scale out
+	Initial time.Duration
+	// Jitter value randomizes an additional delay between 0 and Jitter
+	Jitter time.Duration
+	// Max maximum values of the backoff
+	Max time.Duration
 }
 
 // Returns the current value of the counter and then multiplies it
 // Factor
-func (b *backoff) Duration() time.Duration {
-	//Zero-values are nonsensical, so we use
-	//them to apply defaults
-	if b.Min == 0 {
-		b.Min = 100 * time.Millisecond
-	}
+func (b *backoff) Duration() (dur time.Duration) {
+	// Zero-values are nonsensical, so we use
+	// them to apply defaults
 	if b.Max == 0 {
 		b.Max = 10 * time.Second
 	}
-	if b.Factor == 0 {
-		b.Factor = 2
+
+	if b.Initial == 0 {
+		b.Initial = 100 * time.Millisecond
 	}
-	//calculate this duration
-	dur := float64(b.Min) * math.Pow(b.Factor, float64(b.attempts))
-	if b.Jitter {
-		dur = rand.Float64()*(dur-float64(b.Min)) + float64(b.Min)
+
+	// calculate this duration
+	if dur = time.Duration(1 << uint(b.attempts)); dur > 0 {
+		dur = dur * b.Initial
+	} else {
+		dur = b.Max
 	}
-	//cap!
-	if dur > float64(b.Max) {
-		return b.Max
+
+	if b.Jitter > 0 {
+		dur = dur + time.Duration(rand.Intn(int(b.Jitter)))
 	}
-	//bump attempts count
+
+	// bump attempts count
 	b.attempts++
-	//return as a time.Duration
-	return time.Duration(dur)
+
+	return dur
 }
 
 //Resets the current value of the counter back to Min